Huaqiangbei , home to the world’s biggest electronics wholesale market, remains shut this week, as the southern city of Shenzhen intensifies efforts to stop the spread of the highly contagious Omicron Covid-19 variant in China’s Silicon Valley . Shenzhen, the richest city in southern Guangdong province, is conducting targeted lockdowns of various communities and office buildings, and massive testing among its 17.6 million residents, as well as requiring negative nucleic acid test results for all bus and Shenzhen Metro train passengers. That means Huaqiangbei will remain closed for “at least three more days”, according to a notice by the electronics retail area’s community on Monday. Business at the Futian subdistrict was initially suspended for four days from last Thursday, after one confirmed Covid-19 case was found to have visited an office building and a mall in the area. “The pandemic control authority of the [Futian] district will conduct scientific research and discuss reopening plans based on new development in the Covid-19 situation,” the Huaqiangbei community said. “Market managers, please appease the [affected] merchants and require them to take Covid-19 tests every day.” The pandemic control team in Huaqiangbei said it had filed an application for the area to reopen last Saturday, but experts determined that risks remained high and postponed the resumption of business, according to the notice cited by market operator Huaqiang Electronics World. The temporary closure affects an important segment of Shenzhen’s hi-tech industry, which accounted for 20 per cent of the city’s gross domestic product in 2020, according to official data. A number of residential buildings in Futian and Nanshan, two of the nine districts comprising Shenzhen, have already been put under lockdown, which has grounded tens of thousands of residents. Lockdowns, closures and repeated testing have become part of the “new normal” for mainland Chinese residents and businesses under Beijing’s “zero-tolerance” policy on the coronavirus, which is in contrast to countries like Singapore that have adopted a “living with Covid-19” approach. Such tight controls on the mainland have shown signs of initial success in fighting the spread of Omicron. On Monday, Shenzhen reported just 13 new local cases among close contacts of confirmed patients and from mass screening. China’s crop of new coronavirus cases defies ‘zero tolerance’ strategy Some of Shenzhen’s most densely populated districts, such as Nanshan, have relaxed the requirement for entry into residential communities to having a negative test result within 48 hours, compared to last week’s 24-hour requirement. Still, a new surge in Covid-19 cases are occurring across China, despite the country’s zero-tolerance strategy. The country reported 526 new infections on Monday – the highest daily infection number since the initial outbreak in Wuhan, capital of central Hubei province, was contained in early 2020. Shenzhen’s zero coronavirus approach is now facing a challenge from neighbouring Hong Kong, where 25,150 new Covid-19 cases were confirmed on Monday . China’s zero-Covid policy to stay but may be fine-tuned, premier says Over the weekend, Shenzhen updated its rules for visitors from Hong Kong. Visitors are required to present Covid-19 test results from one of 33 designated testing organisations in Hong Kong, with clearly stated time and sample method. Starting this month, Shenzhen requires cross-border drivers to show a negative nucleic acid test result within 24 hours and undergo two further tests upon entering. These drivers are also restricted inside a “closed loop” , which bars them from entering any communities or public places on the mainland.